In general, ranking, as applied to a set of objects, indicates the relationships between the objects such that, for any two objects from the set, the first object is either ranked higher than, ranked lower than, or ranked equal to the second object. Often, the ranking of a set of objects is determined with respect to a particular reference such that the ranks of any two objects from the set indicate whether the first object is more preferred than, less preferred than, or equally preferred as the second object with respect to the reference.
Ranking has many applications. For example, a common application of ranking is in the field of Internet search. The Internet provides access to a vast amount of information. The information is stored at many different sites, e.g., on computers and servers and in databases, around the world. These different sites are communicatively linked to the Internet via various network infrastructures. People, i.e., Internet users, may access the publicly available information on the Internet via various suitable network devices connected to the Internet, such as, for example, computers and telecommunication devices.
Due to the sheer amount of information available on the Internet, it is impractical as well as impossible for an Internet user to manually search throughout the Internet for specific pieces of information. Instead, most Internet users rely on different types of computer-implemented tools to help them locate the desired information. One of the most convenient and widely used tools is a search engine, such as the search engines provided by Yahoo!® Inc. (http://search.yahoo.com), Google™ (http://www.google.com), and Microsoft® Inc. (http://search.live.com).
To search for the information relating to a specific topic or subject matter, an Internet user provides a short phrase consisting of one or more words, often referred to as a “search query”, to a search engine. The search query typically describes the topic or subject matter. The search engine conducts a search based on the search query using various search algorithms to identify one or more Internet contents most likely to be related to the topic or subject matter described by the search query. Internet contents are data or information available on the Internet and may be in various formats, such as texts, audios, videos, graphics, etc. The search engine usually arranges, i.e., ranks, the identified Internet contents according to their degrees of relevance to the search query such that an Internet content that is relatively more relevant to the search query is ranked higher and presented before an Internet content that is relatively less relevant to the search query. In this case, an Internet content that is relatively more relevant to the search query is more preferred with respect to the search query than an Internet content that is relatively less relevant to the search query.
The identified Internet contents arranged in an order of relevance with respect to the search query is often referred to as a “search result” obtained in response to the search query. The search result may then be presented to the user requesting the search, often in the form of a list of clickable links, each link being associated with a different web page containing some of the Internet contents identified by the search engine. The user then is able to click on the individual links to view the specific contents as he wishes.
There are continuous efforts to improve the performance qualities of the search engines. Accuracy, completeness, presentation order, and speed are but a few aspects of the search engines for improvement.